The female genital mucosa is a major route of infection for HIV. This proposal will address significant gaps in knowledge regarding T cell immunobiology within the female reproductive tract. Fundamental issues, including memory CD8 and CD4 T cell differentiation, maintenance, trafficking, function, and contribution to protection will be addressed in a high-throughput tractable mouse model. Ex vivo analyses of memory T cell differentiation state, and function will be complemented by static and intravital imaging to yield a more complete anatomic picture of T cell immunobiology and APC/antigen trafficking within this complex organ system. Mechanisms underlying recently discovered functions of local memory T cells, including the ability to potentiate rapid peripheral T cell recruitment and activate the local innate immune system, will be defined. Memory T cell recirculation patterns through various compartments of the female reproductive tract will be defined by parabiosis. Contributions of local and peripheral memory T cell populations to protection against genital viral re-challenge will be assessed. These investigations will inform the development of T cell vaccines that rapidly intercept HIV upon exposure within the female reproductive tract by providing new insight into the regulation, function and protective mechanisms of cellular immunity at this site.